1. Field of the Invention
The present invention relates to a device for removing and/or injecting a fluid such as a gas, a liquid, or a gas-liquid mixture which is in a given state, without disturbing this state.
The word "state" is intended to signify for example a state of equilibrium in which a fluid.
2. Description of the Prior Art
When a fluid, for example a noncondensable gas or liquid with a low viscosity, is analyzed in a temperature range between 0 and 40.degree. C., the sample removal stage does not introduce any marked change into the composition of these fluids. Generally such sampling is done by drawing samples up into a pipes of the sampling units by means of a syringe. The fluids to be analyzed can be mixtures of gases such as oxygen, nitrogen, carbon dioxide, carbon monoxide, methane, ethane, or liquids whose boiling points are greater than room temperature and liquids with low viscosity, less than 20 centistokes for example.
When the fluids include products or components that can react with each other when an external parameter varies, for example a thermodynamic parameter, the chemical and/or thermodynamic equilibrium may shift irreversibly, modifying the nature of the fluid and leading to a non-representative analysis of the fluid.
This change in nature may be encountered in mixtures containing condensable products such as H.sub.2 O, SO.sub.2, pentane, or butane in specific temperature ranges, heavy hydrocarbons in the presence of noncondensable products, or more generally products whose compositions at equilibrium may change with temperature or pressure, such as azeotropes.
This is the case for example of a gas containing hydrogen sulfide and sulfur dioxide SO.sub.2 that react in the balanced reaction 2 H.sub.2 S+SO.sub.2 .fwdarw.3 S+2 H.sub.2 O. A drop in temperature shifts the reaction rightward leading to production of liquid or solid sulfur and water. The analysis of this gas is not representative because sulfur and water are added in the analysis to the initial components H.sub.2 S and SO.sub.2.
This is also the case when analyzing combustion fumes containing sulfur dioxide and large quantities of water. A drop in temperature below the dewpoint inevitably causes the content of the gas, SO.sub.2, and SO.sub.3 sampled to drop, causing an error in quantifying the components of these fumes, possibly a large error.
For liquids at risk of crystallizing or demixing (separation of liquid into several phases) when the temperature varies or liquids with high viscosities, the change in composition upon sampling may bring about substantial analysis errors.
It is thus desirable to have a device that will enable a fluid sample to be removed under conditions that will prevent any conversion of the fluid and store the fluid in a state substantially identical to the original state.
The prior art describes various types of devices for injecting and/or sampling products.
U.S. Pat. No. 4,684,344 describes a syringe comprising a heating means with a point action, namely concentrated more particularly in one spot. Contrary to the principle employed in the present invention, the teaching of this document is to cause a change in state of a product to bring it into a form in which it can be injected.
Due to industrial constraints demanding increasingly fine and precise analyses, it is desirable to have a device that will sample and/or inject a fluid whose state is likely to evolve due to for example a change in at least one thermodynamic parameter, while keeping this fluid in a given state.
The state of the fluid to be stored may correspond to a state of equilibrium which is the original state of the fluid in a processing unit.